A 13-Week Oral Repeated Dose Toxicity Study of (±)-4-Diethylamino-1, 1-Dimethylbut-2-Yn-1-Yl 2-Cyclohexyl-2-Hydroxy-2-Phenylacetate Monohydrochloride Monohydrate (Ns-21), a Novel Drug for Urinary Frequency and Incontinence, in Rats Followed by a 5-Week Recovery Test

Abstract

A 13-week oral repeated dose toxicity study of (+/-)-4-diethylamino-1,1-dimethylbut-2-yn-1-yl 2-cyclohexyl-2-hydroxy-2-phenylacetate monohydrochloride monohydrate (NS-21), a new drug for the treatment of urinary frequency and incontinence, was conducted in Sprague-Dawley rats. Male and female rats were given the drug orally for 13 weeks at doses of 0 (control), 6, 30, 150 and 750 mg/kg. After discontinuation of the treatment, a 5-week recovery test was also conducted at doses of 0, 30, 150 and 750 mg/kg. Nine cases of death occurred in the 750 mg/kg group. Main pathological findings in these cases were congestion and edema in lung. Mydriasis, salivation, lacrimation and a decrease in body weight or a suppression of its weight gain were seen in the 30 mg/kg group and over. Piloerection and an increase in water consumption were seen in the 150 and 750 mg/kg groups. In addition, a decrease in spontaneous locomotor activity, abdominal distention, unkempt fur, soft stool, diarrhea and decreases in feces and food consumption were seen in the 750 mg/kg group. Ophthalmologic examination confirmed mydriasis and lacrimation in the 30 mg/kg group and over. Urinalysis showed decreases in Na+ and K+ excretions in the 30 mg/kg group and over, an increase in urinary protein in the 150 and 750 mg/kg groups, and a decrease in urine volume in the 750 mg/kg group. Hematological examination showed decreases in hemoglobin and hematocrit in the 150 and 750 mg/kg groups, and a decrease in lymphocytes in the 750 mg/kg group. Blood chemical examination showed an increase in total protein in the 30 mg/kg group and over, a decrease in triglyceride in the 150 and 750 mg/kg groups, and an increase in BUN in the 750 mg/kg group. Pathological examination disclosed hepatocellular hypertrophy caused by hyperplasia of smooth-ER in the 30 mg/kg group and over, and a decrease in number of glycogen granules in the 150 and 750 mg/kg groups. Stimulated thyroid follicles were seen in the 30 mg/kg group and over. Increases in incidence and severity of chronic progressive nephropathy were observed in the 150 and 750 mg/kg groups. Ultrastructual features of the renal lesions were swelling and foot process loss of the glomerular epithelial cells, absorption droplets in the glomerular epithelial cells, increase of lysosomes in the proximal tubular cells and hyaline casts in the tubular lumen. Adrenocortical hypertrophy was seen in the 150 and 750 mg/kg groups. In the 750 mg/kg group, a decrease of hematopoietic tissue in bone marrow and thymic and testicular tubular atrophy were observed. The recovery test showed that the above-mentioned changes were satisfactorily reversible or the degree and frequency of these changes were lowered. No treatment-related effects were seen in the 6 mg/kg group. These results show that the NOAEL (no observed adverse effect level) of NS-21 is 6 mg/kg for 13-week oral toxicity in rats.

Relation between statistics and treatment-related changes obtained from toxicity studies in rats: if detected a significant difference in low or middle dose for quantitative values, this change is considered as incidental change?

“…Presence of dose-related pattern, visually Nishiguchi et al, 1997;Nishiguchi et al, 1994;Takagi et al, 1992b;Nakano et al, 1992;Tamura et al, 1983;Yamazaki et al, 2005;Chemical product Safety Center, et al, 2007;Topping et al, 2007;Guijie et al, 2006;Poon et al, 1998;McClain et al, 2006;Sato et al, 2007;Hellwig et al, 1993;Webb et al, 1993;Mellert et al, 2002;Bär et al, 1995;Arterburn et al, 2000;Goldsmith, 2000;Lee et al, 2004;Janssen et al, 2000;Kanki et al, 2003;O'Hagan and Menzel, 2003;Nakamura et al, 2001;Thomas et al, 1991;Abdo et al, 1986;Morgan et al, 1989;Dunnick et al, 1987;Okazaki et al, 2002;Okazaki et al, 1993;Kato et al, 1993;Jeong et al, 2006;Shim et al, 2003 No change in a related parameter Inui et al, 1997;Takeuchi et al, 1985;Jonker et al, 1993;MacKenzie et al, 1992a;Barber and Topping, 1995;Oshima et al, 1999;Suzuki et al, 1997;Graça et al, 2007;Shimpo et al, 1990 High or low value of control group Inui et al, 1997;…”